Fix flaky test

Author: MackinnonBuck

tests/ModelContextProtocol.AspNetCore.Tests/ResumabilityIntegrationTests.cs

@@ -344,6 +344,9 @@ public async Task Client_CanResumeUnsolicitedMessageStream_AfterDisconnection()
             return default;
         });
 
+        // Wait for the client's GET SSE stream to be established before sending notifications
+        await faultingStreamHandler.WaitForStreamAsync(TestContext.Current.CancellationToken);
+
         // Send a custom notification to the client on the unsolicited message stream
         await server.SendNotificationAsync(CustomNotificationMethod, new JsonObject { ["message"] = InitialMessage }, cancellationToken: TestContext.Current.CancellationToken);
 

tests/ModelContextProtocol.AspNetCore.Tests/Utils/FaultingStreamHandler.cs

@@ -11,6 +11,10 @@ internal sealed class FaultingStreamHandler : DelegatingHandler
 {
     private FaultingStream? _lastStream;
     private TaskCompletionSource? _reconnectTcs;
+    private TaskCompletionSource _streamAvailableTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
+
+    public Task WaitForStreamAsync(CancellationToken cancellationToken = default)
+        => _streamAvailableTcs.Task.WaitAsync(cancellationToken);
 
     public async Task<ReconnectAttempt> TriggerFaultAsync(CancellationToken cancellationToken)
     {
@@ -24,6 +28,7 @@ public async Task<ReconnectAttempt> TriggerFaultAsync(CancellationToken cancella
             throw new InvalidOperationException("Cannot trigger a fault while already waiting for reconnection.");
         }
 
+        _streamAvailableTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
         _reconnectTcs = new();
         await _lastStream.TriggerFaultAsync(cancellationToken);
 
@@ -63,6 +68,8 @@ protected override async Task<HttpResponseMessage> SendAsync(
             }
 
             response.Content = newContent;
+
+            _streamAvailableTcs.TrySetResult();
         }
 
         return response;